1. Field of the Invention
The present invention is related to a method and device of gate driving, and more particularly, to a method and device of gate driving which adjust gate driving signals through charge recycling and reutilization.
2. Description of the Prior Art
A liquid crystal display (LCD) monitor has characteristics of light weight, low power consumption, zero radiation, etc. and is widely used in many information technology (IT) products, such as computer systems, mobile phones, and personal digital assistants (PDAs). The operating principle of the LCD monitor is based on the fact that different twist states of liquid crystals result in different polarization and refraction effects on light passing through the liquid crystals. Thus, the liquid crystals can be used to control amount of light emitted from the LCD monitor by arranging the liquid crystals in different twist states, so as to produce light outputs at various brightnesses, and diverse gray levels of red, green and blue light.
Please refer to FIG. 1, which is a schematic diagram of a thin film transistor (TFT) LCD monitor 10 of the prior art. The LCD monitor 10 includes an LCD panel 100, a source driver 102, a gate driver 104 and a voltage generator 106. The LCD panel 100 is composed of two substrates, and space between the substrates is filled with liquid crystal materials. One of the substrates is installed with a plurality of data lines 108, a plurality of scan lines (or gate lines) 110 and a plurality of TFTs 112, and another substrate is installed with a common electrode for providing a common signal Vcom outputted by the voltage generator 106. The TFTs 112 are arranged as a matrix on the LCD panel 100. Accordingly, each data line 108 corresponds to a column of the LCD panel 100, each scan line 100 corresponds to a row of the LCD panel 100, and each TFT 112 corresponds to a pixel. Note that the LCD panel 100 composed of the two substrates can be regarded as an equivalent capacitor 114.
In FIG. 1, the gate driver 104 sequentially generate the gate driving signals VG_1-VG_M to row by row activate the TFTs 112 and update pixel data stored in the equivalent capacitors 114. In detail, please refer to FIG. 2, which is a schematic diagram of the gate driver 104. The gate driver 104 includes a logic circuit 105 and buffers 107_1-107_M. Load modules 109_1-109_M are equivalent circuits of loads. The logic circuit 105 controls transistor switches of the buffers 107_1-107_M to alternatively provide a high voltage VGG or a low voltage VEE to the load modules 109_1-109_M, so as to create square waves of the gate driving signals VG_1-VG_M.
However, since parasitical capacitors exist between the equivalent capacitors 114 and gates of the TFTs 112, variations of the gate driving signals VG_1-VG_M couple into the equivalent capacitors 114 via the parasitical capacitors during backward edges of the square waves of the gate driving signals VG_1-VG_M, such that the equivalent capacitors 114 store image contents with biases. In order to the coupling effect, the gate driver 104 adjusts waveforms of the square waves of the gate driving signals VG_1-VG_M, as illustrated in FIG. 3. As a result, instant variations of the gate driving signals VG_1-VG_M no longer affect the image contents stored in the equivalent capacitors 114. Certainly, to generate the waveform shown in FIG. 3, the gate driver 104 has to include additional control circuits.
Therefore, adjusting the waveforms of the gate driving signals more economically has been a major focus of the industry.